Bug Description

Options I can think of:

1 - As soon as the user lands his finger (touch down) outside the area of the focused text entry

Motivation: if the user touches outside the focused text entry it means he's no longer interested in it so unfocus it in order to make the virtual keyboard get ouf of the way, giving the user more space for whatever he's now up to.

2 - As soon as the user taps (ie, touch down & touch up over roughly the same item) outside the area of the focused text entry

Motivation: Sometimes, while filling out a text entry, you might want to peek at content currently out of sight and therefore scroll up or down a bit. E.g. text entries in a long web form where you might want to read some explanation above or below that text entry, or even the title tied to it might be out of sight so you might want to scroll up a bit to recall what that text entry is about. In such situations, unfocusing the text entry and therefore hiding the virtual keyboard might be disruptive.

Motivation 2: flicking up or down to scroll content is an interaction that doesn't change the state of the content itself, just like moving a mouse pointer around the screen. So having the text entry unfocused just because the content was scrolled would break that paradigm.